Today, various types of physical quantity sensors are used. Especially, many proposals are made for the correction of the sensor output of an angular rate sensor typified by a vibratory gyroscope (gyro).
In the prior-art technology described in Patent Document 1, a technique is proposed for changing the detection sensitivity (scale factor) of a physical quantity sensor proportional to a variation in the power supply voltage at which the physical quantity sensor operates. As shown in FIG. 10, this prior-art physical quantity sensor has the configuration in which the output signal of a sensor element 1 detected by a detection circuit 2 is further amplified by an amplifier circuit 6 for output.
As the amplifier circuit 6, an inverting amplifier circuit implemented by an OP Amp 4 is used where a MOS element 7 is used as the input resistor and a resistor element 8 is used as the feedback resistor. The gate voltage of this MOS element 7 is biased by the voltage that varies according to the power supply voltage of the physical quantity sensor to allow the detection sensitivity of the physical quantity sensor to be adjusted and, especially, the detection sensitivity of the physical quantity sensor to be varied proportion to a variation in the power supply voltage.
These characteristics, known as ratiometric, are useful characteristics for digitally processing the output signal of a physical quantity sensor outside the sensor. That is, combining a physical quantity sensor having those output characteristics with a ratiometric-compatible A/D conversion circuit, whose conversion resolution varies proportional to the power supply voltage of the sensor, allows for an configuration where the A/D converted output data is not affected by a variation in the power supply voltage when a physical quantity is applied to the sensor.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-53396 (pp. 4-6, FIG. 1)